CVE-2018-1000836: Bw calendar engine XML External Entity (XXE) Vulnerability Vulnerability

CRITICAL
Advisory Identifier: GHSA-xmvg-w4f9-99r7
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CVSS 9.0
CWE-611
Published
Advisory Summary

CVE-2018-1000836 is a CRITICAL (CVSS 9.0) xml external entity (xxe) vulnerability vulnerability (CWE-611: Improper Restriction of XML External Entity Reference) affecting Bw calendar engine libraries in the Maven ecosystem. The issue involves xml external entity (xxe) vulnerability in bw-calendar-engine. Remediation is available in the latest vendor maintenance releases.

CVE-2018-1000836 at a Glance

CVE Identifier CVE-2018-1000836
GHSA Identifier GHSA-xmvg-w4f9-99r7
Severity CRITICAL
CVSS v3.1 Base Score 9.0
CWE Classification CWE-611: Improper Restriction of XML External Entity Reference
Affected Product Bw calendar engine
Package Ecosystem Maven
Published Date
Last Updated

Security Impact

CVSS: 9.0

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H).

Attack Vector Network (AV:N)
Attack Complexity High (AC:H)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Changed (S:C)
Confidentiality High (C:H)
Integrity High (I:H)
Availability High (A:H)

How to Fix CVE-2018-1000836

To remediate this vulnerability, upgrade all affected Bw calendar engine dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

org.bedework.caleng:bw-calendar-engine fixed: Latest secure release 
<dependency>
    <groupId>org.bedework.caleng</groupId>
    <artifactId>bw-calendar-engine</artifactId>
    <version>Latest secure release</version>
</dependency>
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

mvn dependency:tree -Dincludes=org.bedework.caleng

How to Check if You Are Affected

To determine whether your Java application is affected by CVE-2018-1000836, inspect your build dependencies using the Maven Dependency Plugin:

mvn dependency:tree -Dincludes=org.bedework.caleng

Analyze the terminal output to locate any version of Bw calendar engine in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than the patched release), your application is affected.

Note: The mvn dependency:tree -Dincludes=org.bedework.caleng command inspects the resolved dependency graph declared in your project's POM files; it does not perform automated security scanning or inspect runtime dynamic classpaths. Always verify runtime container classpaths and shaded JARs.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-611: Improper Restriction of XML External Entity Reference, where the product processes an xml document that can contain xml entities with uris that resolve to documents outside of the intended sphere of control, causing the product to embed incorrect documents into its output. In Bw calendar engine, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

bw-calendar-engine version <= bw-calendar-engine-3.12.0 contains a XML External Entity (XXE) vulnerability in IscheduleClient XML Parser that can result in Disclosure of confidential data, denial of service, SSRF, port scanning. This attack appear to be exploitable via Man in the Middle or malicious server.

CVE-2018-1000836 Affected Bw calendar engine Versions

1 component(s)
Product / Package Ecosystem Affected Versions Fixed Version
org.bedework.caleng:bw-calendar-engine
maven/org.bedework.caleng/bw-calendar-engine
Maven
≤ 3.12.2

References

NVD — CVE-2018-1000836 NVD
https://nvd.nist.gov/vuln/detail/CVE-2018-1000836
Bw calendar engine Source Repository REPOSITORY
https://github.com/Bedework/bw-calendar-engine/issues/3
0dd.zone/2018/10/28/bw-calen... WEB
https://0dd.zone/2018/10/28/bw-calendar-engine-XXE-MitM
Bw calendar engine Source Repository REPOSITORY
https://github.com/Bedework/bw-calendar-engine
GitHub Advisory / Wiki ADVISORY
https://github.com/advisories/GHSA-xmvg-w4f9-99r7

Frequently Asked Questions

What is CVE-2018-1000836?
CVE-2018-1000836 is a security vulnerability in Bw calendar engine involving XML External Entity (XXE) vulnerability in bw-calendar-engine under CWE-611: Improper Restriction of XML External Entity Reference.
Which Bw calendar engine versions are affected?
Affected versions include releases prior to current release patches across affected packages: org.bedework.caleng:bw-calendar-engine.
What version fixes CVE-2018-1000836?
Upgrading to current release patches (or the latest patched release for your respective branch) resolves the vulnerability.
Is bw-calendar-engine affected?
Yes, org.bedework.caleng:bw-calendar-engine is affected in releases prior to Latest secure release. Upgrade your dependency to Latest secure release or later.
What is the CVSS score of CVE-2018-1000836?
CVE-2018-1000836 has a CVSS v3.1 base score of 9.0 (CRITICAL) with vector string CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H.
What CWE is associated with CVE-2018-1000836?
CVE-2018-1000836 is classified under CWE-611: Improper Restriction of XML External Entity Reference (The product processes an XML document that can contain XML entities with URIs that resolve to documents outside of the intended sphere of control, causing the product to embed incorrect documents into its output.).
How can I check Maven dependencies for CVE-2018-1000836?
Run the dependency tree command: 'mvn dependency:tree -Dincludes=org.bedework.caleng'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-xmvg-w4f9-99r7",
  "modified" : "2022-09-14T22:23:07Z",
  "published" : "2018-12-20T22:02:51Z",
  "aliases" : [ "CVE-2018-1000836" ],
  "summary" : "XML External Entity (XXE) vulnerability in bw-calendar-engine",
  "details" : "bw-calendar-engine version <= bw-calendar-engine-3.12.0 contains a XML External Entity (XXE) vulnerability in IscheduleClient XML Parser that can result in Disclosure of confidential data, denial of service, SSRF, port scanning. This attack appear to be exploitable via Man in the Middle or malicious server.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "org.bedework.caleng:bw-calendar-engine"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "last_affected" : "3.12.2"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2018-1000836"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/Bedework/bw-calendar-engine/issues/3"
  }, {
    "type" : "WEB",
    "url" : "https://0dd.zone/2018/10/28/bw-calendar-engine-XXE-MitM"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/Bedework/bw-calendar-engine"
  }, {
    "type" : "ADVISORY",
    "url" : "https://github.com/advisories/GHSA-xmvg-w4f9-99r7"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-611" ],
    "severity" : "CRITICAL",
    "github_reviewed" : true,
    "github_reviewed_at" : "2020-06-16T22:03:50Z",
    "nvd_published_at" : null
  }
}